You didn't know? It's in the game docs.
You are going to be so surprised when you realize that I didn't invent the navy rules. Check out this thread.
https://www.simcountry.com/discus/messages/1/22947.html?1384496505 Where I say:
"The navy should fall somewhere as being somewhat less efficient in combat as land-based fighter and bombers with the advantage of global mobility."
"any adjustments should not increase their combat ability beyond land-based air weapons"
"Navies fighters are not a unit to replace roles of everything else."
"I would expect though, for a player with a very good defense like you described, that a navy only strategy would be less effective."
"a heavily defended country, affordable by few players, which would and should take considerable effort to take. I think it is okay if such a target is very inefficiently taken with navy firepower alone. "
"Why should navies, with their immense range, be any better than land units or land-based air power?"
"I don't think naval units should be unstoppable unlimited range weapons of doom"
"Weapons should be balanced by being effective in different roles and relative to their cost. "
"if the navy is as effective (or more effective) as a land-based air unit or a ground unit, why would one purchase those units over naval units?"
Where was anyone else with these views then? I now have "bad form" because I didn't remind my enemies about the power of navies on the eve of war? The same guys who used navies themselves on an ally of mine recently.
That's kinda a stretch. You think?